Scroll machine having counterweights with changeable cavity

ABSTRACT

A balancing system for different compressors utilizes a counterweight having a common exterior configuration. The mass of the counterweight is optimized for each compressor by changing the size of a recess located in the counterweight. In one embodiment, the recess is an arcuately shaped recess; and in another embodiment, the recess is a plurality of holes.

FIELD OF THE INVENTION

The present invention relates to the balancing of rotary machines. Moreparticularly, the present invention relates to counterweights which areused to balance rotary machines where the counterweight includes avariable sized cavity which is used to optimize the mass of thecounterweight.

BACKGROUND AND SUMMARY OF THE INVENTION

A class of machines exists in the art generally known as “scroll”apparatus for the displacement of various types of fluids. Suchapparatus may be configured as an expander, a displacement engine, apump, a compressor, etc., and many features of the present invention areapplicable to any one of these machines. For purposes of illustration,however, the disclosed embodiments are in the form of a hermeticrefrigerant compressor.

Generally speaking, a scroll apparatus comprises two spiral scroll wrapsof similar configuration, each mounted on a separate end plate to definea scroll member. The two scroll members are interfitted together withone of the scroll wraps being rotationally displaced 180 from the other.The apparatus operates by orbiting one scroll member (the “orbitingscroll”) with respect to the other scroll member (the “fixed scroll” or“non-orbiting scroll”) to make moving line contacts between the flanksof the respective wraps, defining moving isolated crescent-shapedpockets of fluid. The spirals are commonly formed as involutes of acircle, and ideally there is no relative rotation between the scrollmembers during operation; i.e., the motion is purely curvilineartranslation (i.e., no rotation of any line in the body). The fluidpockets carry the fluid to be handled from a first zone in the scrollapparatus where a fluid inlet is provided, to a second zone in theapparatus where a fluid outlet is provided. The volume of a sealedpocket changes as it moves from the first zone to the second zone. Atany one instant in time, there will be at least one pair of sealedpockets; and when there are several pairs of sealed pockets at one, eachpair will have different volumes. In a compressor, the second zone is ata higher pressure than the first zone and is physically locatedcentrally in the apparatus, the first zone being located at the outerperiphery of the apparatus.

Two types of contacts define the fluid pockets formed between the scrollmembers: axially extending tangential line contacts between the spiralfaces or flanks of the wraps caused by radial forces (“flank sealing”),and area contacts caused by axial forces between the plane edge surfaces(the “tips”) of each wrap and the opposite end plate (“tip sealing”).For high efficiency, good sealing must be achieved for both types ofcontacts.

The concept of a scroll-type apparatus has, thus, been known for sometime and has been recognized as having distinct advantages. For example,scroll machines have high isentropic and volumetric efficiency, and,hence, are relatively small and lightweight for a given capacity. Theyare quieter and more vibration-free than many compressors because theydo not use large reciprocating parts (e.g., pistons, connecting rods,etc.), and because all fluid flow is in one direction with simultaneouscompression in plural opposed pockets, there are less pressure-createdvibrations. Such machines also tend to have high reliability anddurability because of the relatively few moving parts utilized, therelatively low velocity of movement between the scrolls, and an inherentforgiveness to fluid contamination.

The orbiting of the one scroll member with respect to the other scrollmember creates an imbalance which is typically counteracted using one ormore counterweights. When designing new compressors and/or redesigningand modifying existing compressors, it is sometimes necessary to designa new counterweight. The need for a new counterweight is typicallyrequired when the mass of the counterweight needs to be optimized for aspecific application. Each time a new counterweight of a new mass isrequired, new molds for the counterweight of the specific mass must bedeveloped. The development of the new molds incurs development time andcapital costs associated with the new mold.

The present invention provides the art with a counterweight whichincludes a recess. The size and/or depth of the recess can be varied tovary the mass of the counterweight. Thus, a counterweight having commonouter dimensions can be manufactured in various masses by changing thesize and/or depth of the recess in the counterweight to meet therequired mass for the counterweight. The fact that counterweights havingdifferent masses can still maintain common outer dimensions eliminatesthe need for the tooling on the assembly line which assemble thecounterweights to the compressor assembly to be modified and/or changedwhen different masses of counterweights are used.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a vertical cross-sectional view through the center of ascroll-type refrigeration compressor incorporating the variable masscounterweights in accordance with the present invention;

FIG. 2 is a perspective view looking down on the counterweightillustrated in FIG. 1 and the mold or die used to manufacture thecounterweight;

FIG. 3 is a perspective view looking up on the counterweight and mold ordie illustrated in FIG. 2;

FIG. 4 is a view similar to FIG. 3, but showing the counterweight havinga different mass;

FIG. 5 is a perspective view looking up on a counterweight and formingmold or die in accordance with another embodiment of the presentinvention;

FIG. 6 is a perspective view of a mold assembly which produces thecounterweight illustrated in FIGS. 2 and 3; and

FIG. 7 is a perspective view of a mold assembly which produces thecounterweight illustrated in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

The balancing system of the present invention is applicable to any typeof rotary apparatus. For exemplary purposes only, the present inventionis described in conjunction with a rotary compressor and, in particular,with a scroll-type refrigerant compressor.

Referring now to the drawings in which like reference numerals designatelike or corresponding parts throughout the several views, there is shownin FIG. 1 a scroll compressor which incorporates the balancing system inaccordance with the present invention which is designated generally byreference numeral 10. Compressor 10 comprises a generally cylindricalhermetic shell 12 having welded at the upper end thereof a cap 14 and atthe lower end thereof a base 16 having a plurality of mounting feet (notshown) integrally formed therewith. Cap 14 is provided with arefrigerant discharge fitting 18 which may have the usual dischargevalve therein (not shown). Other major elements affixed to the shellinclude a transversely extending partition 22, which is welded about itsperiphery at the same point that cap 14 is welded to shell 12 a mainbearing housing 24 which is suitably secured to shell 12 and a lowerbearing housing 26 also having a plurality of radially outwardlyextending legs, each of which is also suitably secured to shell 12. Amotor stator 28, which is generally square in cross-section but with thecorners rounded off, is press fitted into shell 12. The flats betweenthe rounded corners on the stator provide passageways between the statorand shell, which facilitate the return flow of lubricant from the top ofthe shell to the bottom.

A drive shaft or crankshaft 30 having an eccentric crank pin 32 at theupper end thereof is rotatably journaled in a bearing 34 in main bearinghousing 24, and a second bearing 36 in lower bearing housing 26.Crankshaft 30 has at the lower end a relatively large diameterconcentric bore 38 which communicates with a radially outwardly includedsmaller diameter bore 40 extending upwardly therefrom to the topcrankshaft 30. Disposed within bore 38 is a stirrer 42. The lowerportion of the interior shell 12 defines an oil sump 44 which is filledwith lubricating oil to a level slightly above the lower end of a rotor46; and bore 38 acts as a pump to pump lubricating fluid up thecrankshaft 30 and into bore 40, and ultimately to all of the variousportions of the compressor which require lubrication.

Crankshaft 30 is rotatively driven by an electric motor including stator28, windings 48 passing therethrough and rotor 46 press fitted on thecrankshaft 30 and having upper and lower counterweights 50 and 52,respectively.

The upper surface of main bearing housing 24 is provided with a flatthrust bearing surface 54 on which is disposed an orbiting scroll member56 having the usual spiral vane or wrap 58 on the upper surface thereof.Projecting downwardly from the lower surface of orbiting scroll member56 is a cylindrical hub having a journal bearing 60 therein, and inwhich is rotatively disposed a drive bushing 62 having an inner bore 64in which crank pin 32 is drivingly disposed. Crank pin 32 has a flat onone surface which drivingly engages a flat surface (not shown) formed ina portion of bore 64 to provide a radially compliant drivingarrangement, such as shown in U.S. Pat. No. 4,877,382, the disclosure ofwhich is hereby incorporated herein by reference. An Oldham coupling 66is also provided, positioned between orbiting scroll member 56 and mainbearing housing 24, and keyed to orbiting scroll member 56 and anon-orbiting scroll member 68 to prevent rotational movement of orbitingscroll member 56. Oldham coupling 66 is preferably of the type disclosedin U.S. Pat. No. 5,320,506, the disclosure of which is herebyincorporated herein by reference.

Non-orbiting scroll member 68 is also provided, having a wrap 70positioned in meshing engagement with wrap 58 of orbiting scroll member56. Non-orbiting scroll member 68 has a centrally disposed dischargepassage 72 which communicates with an upwardly open recess 74 which, inturn, is in fluid communication with a discharge muffler chamber 76defined by cap 14 and partition 22. An annular recess 78 is also formedin non-orbiting scroll member 68 within which is disposed a sealassembly 80. Recesses 74 and 78 and seal assembly 80 cooperate to defineaxial pressure biasing chambers which receive pressurized fluid beingcompressed by wraps 58 and 70 so as to exert an axial biasing force onnon-orbiting scroll member 68 to thereby urge the tips of respectivewraps 58, 70 into sealing engagement with the opposed end platesurfaces. Seal assembly 80 is preferably of the type described ingreater detail in U.S. Pat. No. 5,156,539, the disclosure of which ishereby incorporated herein by reference. Non-orbiting scroll member 68is designed to be mounted to main bearing housing 24 in a suitablemanner such as disclosed in the aforementioned U.S. Pat. No. 4,877,382or U.S. Pat. No. 5,102,316, the disclosure of which is herebyincorporated herein by reference.

Referring now to FIGS. 2 and 3, upper counterweight 50 is illustrated ingreater detail. While the present invention is being described inrelation to upper counterweight 50, it is within the scope of thepresent invention to incorporate the variable mass characteristics ofupper counterweight 50 into lower counterweight 52, if desired.

Upper counterweight 50 is stepped and it comprises a semi-circularC-shaped section or main body 90 having circumferentially opposite endfaces 92 and a pair of opposite circumferentially extended flangepositions 94, each including an opening 96 which is utilized to securecounterweight 50 to rotor 46. C-shaped section 90 has an arcuate bodyportion between end faces 92 which extends circumferentially through anarc of up to, but not exceeding, 180° so as to be disposed entirely onone side of a plane extending along the axis of rotation of rotor 46.Flange portions 94 extend circumferentially from the juncture of endfaces 92 to define an angular extension exceeding 180°.

C-shaped section 90 defines a cavity or recess 98 which is utilized toachieve a specified mass for counterweight 50. Recess 98 extends over aspecified arc and it has a specified depth. Both the length of the arcand the depth of the recess can be varied by having differentinterchangeable cores 100 (FIG. 6), which are inserted into a mold ordie 102 (FIG. 6), which is utilized to manufacture counterweight 50. Inaddition, one or more ribs 104 can be formed to extend into recess 98 toadjust the mass of counterweight 50 to the specified mass. Counterweight50′ illustrated in FIG. 4 has an increased mass when compared to themass of counterweight 50 due to the shorter arc of recess 98, theshorter depth of recess 98 and the addition of one or more ribs 104.This is accomplished by having a different core or pin 100. The exteriorconfiguration of counterweights 50 and 50′ are identical, thus allowingboth counterweights 50 and 50′ to be manufactured in the same mold ordie 102 (FIG. 6) with different cores 100 being utilized to define thedifferent sizes of recess 98. Counterweight 50′ would replacecounterweight 50 when the operating characteristics of compressor 10change, with the change in operating characteristics requiringrebalancing of compressor 10.

Referring now to FIG. 5, a counterweight 150 is illustrated inaccordance with another embodiment of the present invention.Counterweight 150 is the same as counterweight 50, except that recess 98has been replaced with a plurality of holes 198. The plurality of holes198 are circumferentially spaced along C-shaped section 90 and each ofthem has a specified depth. Both the number of holes 198 and the depthof each hole 198 can be independently varied by having a core 200 (FIG.7) having different numbers and lengths of pins 200, which are insertedinto the mold or die 102 (FIG. 7), which is utilized to manufacturecounterweights 150.

Thus, counterweights having common outer dimensions can be manufacturedin different masses. This feature reduces the costs associated withadditional plant capital. Prior art designs of counterweights vary byheight and/or diameter thus requiring the assembly tooling for thecounterweight to be modified or replaced when different masses ofcounterweights are used. By communizing the outer dimensions for aplurality of counterweight masses, a single set of assembly equipmentcan be utilized for all of the plurality of counterweight masses.

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A balancing system for a scroll machine comprising: a shell; a firstscroll member disposed within said shell, said first scroll memberhaving a first end plate and a first spiral wrap projecting outwardlyfrom said first end cap; a second scroll member disposed within saidshell, said second scroll member having a second end plate and a secondspiral wrap projecting outwardly from said second end cap, said secondscroll wrap being intermeshed with said first scroll wrap; a drivemember for causing said scroll members to orbit relative to one anotherwhereby said spiral wraps will create pockets of progressively changingvolume between a suction pressure zone and a discharge pressure zone;and a counterweight associated with said drive member, saidcounterweight having a main body defining a recess, said recess beingselected to optimize the total mass of said counterweight.
 2. Thebalancing system for a scroll machine according to claim 1, wherein saidrecess comprises a plurality of holes.
 3. The balancing system for ascroll machine according to claim 1, wherein said drive member includesa motor having a stator and a rotor, said counterweight being attachedto said rotor.
 4. The balancing system for a scroll machine according toclaim 1, wherein said main body is an arcuate body.
 5. The balancingsystem for a scroll machine according to claim 1, wherein saidcounterweight includes a pair of flanges extending from opposite sidesof said main body, each of said flanges defining a hole for attachingsaid counterweight to said drive member.
 6. A balancing system for ascroll machine comprising: a first shell; a first scroll member disposedwithin said first shell, said first scroll member having a first endplate and a first spiral wrap extending from said first end plate; asecond scroll member disposed within said first shell, said secondscroll member having a second end plate and a second spiral wrapextending from said second end plate; a first drive member for causingsaid first and second scroll members to orbit relative to one anotherwhereby said first and second spiral wraps will create pockets ofprogressively changing volume between a first suction pressure zone andfirst discharge zone; a first counterweight associated with first drivemember, said first counterweight having a first main body defining afirst recess; a second shell; a third scroll member disposed within saidsecond shell, said third scroll member having a third end plate and athird spiral wrap extending from said third end plate; a fourth scrollmember disposed within said second shell, said fourth scroll memberhaving a fourth end plate and a fourth spiral wrap extending from saidfourth end plate; a second drive member for causing said third andfourth scroll members to orbit relative to one another whereby saidthird and fourth spiral wraps will create pockets of progressivelychanging volume between a second suction pressure zone and a seconddischarge zone; a second counterweight associated with second drivemember, said second counterweight having a second main body defining asecond recess; and said first and second main bodies of said first andsecond counterweights having common outer dimensions, said first andsecond recesses defined by said first and second main bodies beingdifferent in size to optimize said first counterweight for said firstand second scroll members and to optimize said second counterweight forsaid third and fourth counterweights.
 7. The balancing system for ascroll machine according to claim 6, wherein said first recess comprisesa plurality of holes.
 8. The balancing system for a scroll machineaccording to claim 7, wherein said second recess comprises a pluralityof holes.
 9. The balancing system for a scroll machine according toclaim 6, wherein said first drive member includes a first motor having afirst stator and a first rotor, said first counterweight being attachedto said first rotor.
 10. The balancing system for a scroll machineaccording to claim 9, wherein said second drive member includes a secondmotor having a second stator and a second rotor, said secondcounterweight being attached to said second rotor.
 11. The balancingsystem for a scroll machine according to claim 6, wherein said firstmain body is a first arcuate body.
 12. The balancing system for a scrollmachine according to claim 11, wherein said second main body is a secondarcuate body.
 13. The balancing system for a scroll machine according toclaim 6, wherein said first counterweight includes a first pair offlanges extending from opposite sides of said first main body, each ofsaid first flanges defining a hole for attaching said firstcounterweight to said first drive member.
 14. The balancing system for ascroll machine according to claim 13, wherein said second counterweightincludes a second pair of flanges extending from opposite sides of saidsecond main body, each of said second flanges defining a hole forattaching said second counterweight to said second drive member.
 15. Thebalancing system for a scroll machine according to claim 6, wherein saidfirst and second scroll members have operating characteristics that aredifferent than operating characteristics of said third and fourth scrollmembers.
 16. A method of balancing a scroll machine comprising:providing a first scroll member; providing a second scroll member;providing a first drive member for causing said first and second scrollmembers to orbit relative to one another; providing a firstcounterweight having a specified outer configuration; optimizing themass of said first counterweight by selecting a first specified size ofa first recess; and forming said first recess within said firstcounterweight.
 17. The method according to claim 16, wherein selectingthe specified size of the first recess includes selecting a specifiednumber and a specified depth for a plurality of holes.
 18. The methodaccording to claim 16, wherein selecting the specified size of the firstrecess includes selecting a length and a depth for the first recess. 19.The method according to claim 16 further comprising: providing a thirdscroll member; providing a fourth scroll member; providing a seconddrive member for causing said third and fourth scroll members to orbitrelative to one another; providing a second counterweight having thespecified outer configuration; optimizing the mass of said secondcounterweight by selecting a second specified size of a second recess,the mass of said second counterweight being different than the mass ofsaid first counterweight; and forming said second recess within saidsecond counterweight.
 20. The balancing system for a scroll machineaccording to claim 10, wherein: selecting the specified size of thefirst recess includes selecting a specified number and a specified depthfor a first plurality of holes; and selecting the specified size of thesecond recess includes selecting a specified number and a specifieddepth for a second plurality of holes.
 21. The method according to claim19, wherein: selecting the specified size of the first recess includesselecting a length and a depth for the first recess; and selecting thespecified size of the second recess includes selecting a length and adepth for the second recess.
 22. The method according to claim 19further comprising providing first operating characteristics for saidfirst and second scroll members and providing second operatingcharacteristics for said third and fourth scroll members, said secondoperating characteristics being different than said first operatingcharacteristics.